This invention relates to a character recognition system for an optical alphanumeric character reader and more particularly to such a system for correctly identifying letters in upper and lower cases and certain symbols.
Roman alphabet includes letters of which the upper and lower cases are shaped similarly to each other such as "C" with "c" and "S" with "s". Some symbols look alike such as "," and "'" while some symbols are easily misidentified as two different symbols such as """ and an arrow. Such characters and symbols cannot be identified easily by an optical character reader merely by matching their images with patterns in a dictionary memory. Prior art systems recognize characters and symbols by determining detection lines from a histogram taken in the horizontal direction from an extracted line as shown in FIG. 12 or by obtaining a threshold value on the basis of line height. If there are no clearly visible valleys in the horizontal histogram as shown in FIG. 13 or if an optimum threshold value cannot be determined from the line height as shown in FIGS. 14A-14C, however, it is actually a very difficult problem to correctly recognize characters and symbols.